Airdropping cargo is a common approach for providing materials or supplies (collectively called “cargo”) to remote or hostile areas for supporting military troops. In military applications, airdropping cargo allows resupplying forward areas where ground transport of the cargo is not feasible. Airdropping cargo can also be used in non-military applications, such as delivery of emergency or relief supplies. Similarly, cargo aircraft can drop cargo in areas where ground transport is not readily possible, or timeliness does not allow for the delay associated with ground transportation of the cargo. While helicopters can also deliver supplies in remote areas, they are often limited as to the weight of the payload they can deliver and their delivery range. Further, they can be more susceptible to ground-to-air attacks.
Airdropping cargo has been facilitated by use of global positioning system (“GPS”) technology allowing accurate indication of the aircraft's current position with respect to the intended drop location. GPS systems provide a specified degree of accuracy or precision depending on whether the systems are designed for military or civilian use. GPS systems for civilian applications are deliberately limited with respect to their precision. GPS systems for military applications allow enhanced precision, although these military GPS receivers are comparatively more expensive. GPS technology has limitations in that GPS signals can be jammed.
While airdrop techniques have been improved by using GPS, even a relatively minor error can result in the cargo being dropped in a location that is hundreds or thousands of feet from the desired location. Complicating the process is that in a hostile environment, it is usually safer for cargo aircraft to travel higher and faster when airdropping cargo. However, the accuracy of airdropped cargo is often facilitated by the aircraft traveling lower and slower, and this increases the risk of an attack on the aircraft.
A system that aids in identifying an airdrop location and that is not susceptible to GPS jamming, would facilitate accurate airdrops of cargo. It is with respect to these and other considerations that the disclosure herein is presented.